﻿/*
 * Copyright 2014 Twitter, Inc
 * This file is a derivative work modified by Ringo Leese
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

namespace Titanium.Web.Proxy.Http2.Hpack;

public static class HpackUtil
{
    // Section 6.2. Literal Header Field Representation
    public enum IndexType
    {
        Incremental, // Section 6.2.1. Literal Header Field with Incremental Indexing
        None, // Section 6.2.2. Literal Header Field without Indexing
        Never // Section 6.2.3. Literal Header Field never Indexed
    }

    public const int HuffmanEos = 256;

    // Appendix B: Huffman Codes
    // http://tools.ietf.org/html/rfc7541#appendix-B
    public static readonly int[] HuffmanCodes =
    {
        0x1ff8,
        0x7fffd8,
        0xfffffe2,
        0xfffffe3,
        0xfffffe4,
        0xfffffe5,
        0xfffffe6,
        0xfffffe7,
        0xfffffe8,
        0xffffea,
        0x3ffffffc,
        0xfffffe9,
        0xfffffea,
        0x3ffffffd,
        0xfffffeb,
        0xfffffec,
        0xfffffed,
        0xfffffee,
        0xfffffef,
        0xffffff0,
        0xffffff1,
        0xffffff2,
        0x3ffffffe,
        0xffffff3,
        0xffffff4,
        0xffffff5,
        0xffffff6,
        0xffffff7,
        0xffffff8,
        0xffffff9,
        0xffffffa,
        0xffffffb,
        0x14,
        0x3f8,
        0x3f9,
        0xffa,
        0x1ff9,
        0x15,
        0xf8,
        0x7fa,
        0x3fa,
        0x3fb,
        0xf9,
        0x7fb,
        0xfa,
        0x16,
        0x17,
        0x18,
        0x0,
        0x1,
        0x2,
        0x19,
        0x1a,
        0x1b,
        0x1c,
        0x1d,
        0x1e,
        0x1f,
        0x5c,
        0xfb,
        0x7ffc,
        0x20,
        0xffb,
        0x3fc,
        0x1ffa,
        0x21,
        0x5d,
        0x5e,
        0x5f,
        0x60,
        0x61,
        0x62,
        0x63,
        0x64,
        0x65,
        0x66,
        0x67,
        0x68,
        0x69,
        0x6a,
        0x6b,
        0x6c,
        0x6d,
        0x6e,
        0x6f,
        0x70,
        0x71,
        0x72,
        0xfc,
        0x73,
        0xfd,
        0x1ffb,
        0x7fff0,
        0x1ffc,
        0x3ffc,
        0x22,
        0x7ffd,
        0x3,
        0x23,
        0x4,
        0x24,
        0x5,
        0x25,
        0x26,
        0x27,
        0x6,
        0x74,
        0x75,
        0x28,
        0x29,
        0x2a,
        0x7,
        0x2b,
        0x76,
        0x2c,
        0x8,
        0x9,
        0x2d,
        0x77,
        0x78,
        0x79,
        0x7a,
        0x7b,
        0x7ffe,
        0x7fc,
        0x3ffd,
        0x1ffd,
        0xffffffc,
        0xfffe6,
        0x3fffd2,
        0xfffe7,
        0xfffe8,
        0x3fffd3,
        0x3fffd4,
        0x3fffd5,
        0x7fffd9,
        0x3fffd6,
        0x7fffda,
        0x7fffdb,
        0x7fffdc,
        0x7fffdd,
        0x7fffde,
        0xffffeb,
        0x7fffdf,
        0xffffec,
        0xffffed,
        0x3fffd7,
        0x7fffe0,
        0xffffee,
        0x7fffe1,
        0x7fffe2,
        0x7fffe3,
        0x7fffe4,
        0x1fffdc,
        0x3fffd8,
        0x7fffe5,
        0x3fffd9,
        0x7fffe6,
        0x7fffe7,
        0xffffef,
        0x3fffda,
        0x1fffdd,
        0xfffe9,
        0x3fffdb,
        0x3fffdc,
        0x7fffe8,
        0x7fffe9,
        0x1fffde,
        0x7fffea,
        0x3fffdd,
        0x3fffde,
        0xfffff0,
        0x1fffdf,
        0x3fffdf,
        0x7fffeb,
        0x7fffec,
        0x1fffe0,
        0x1fffe1,
        0x3fffe0,
        0x1fffe2,
        0x7fffed,
        0x3fffe1,
        0x7fffee,
        0x7fffef,
        0xfffea,
        0x3fffe2,
        0x3fffe3,
        0x3fffe4,
        0x7ffff0,
        0x3fffe5,
        0x3fffe6,
        0x7ffff1,
        0x3ffffe0,
        0x3ffffe1,
        0xfffeb,
        0x7fff1,
        0x3fffe7,
        0x7ffff2,
        0x3fffe8,
        0x1ffffec,
        0x3ffffe2,
        0x3ffffe3,
        0x3ffffe4,
        0x7ffffde,
        0x7ffffdf,
        0x3ffffe5,
        0xfffff1,
        0x1ffffed,
        0x7fff2,
        0x1fffe3,
        0x3ffffe6,
        0x7ffffe0,
        0x7ffffe1,
        0x3ffffe7,
        0x7ffffe2,
        0xfffff2,
        0x1fffe4,
        0x1fffe5,
        0x3ffffe8,
        0x3ffffe9,
        0xffffffd,
        0x7ffffe3,
        0x7ffffe4,
        0x7ffffe5,
        0xfffec,
        0xfffff3,
        0xfffed,
        0x1fffe6,
        0x3fffe9,
        0x1fffe7,
        0x1fffe8,
        0x7ffff3,
        0x3fffea,
        0x3fffeb,
        0x1ffffee,
        0x1ffffef,
        0xfffff4,
        0xfffff5,
        0x3ffffea,
        0x7ffff4,
        0x3ffffeb,
        0x7ffffe6,
        0x3ffffec,
        0x3ffffed,
        0x7ffffe7,
        0x7ffffe8,
        0x7ffffe9,
        0x7ffffea,
        0x7ffffeb,
        0xffffffe,
        0x7ffffec,
        0x7ffffed,
        0x7ffffee,
        0x7ffffef,
        0x7fffff0,
        0x3ffffee,
        0x3fffffff // EOS
    };

    public static readonly byte[] HuffmanCodeLengths =
    {
        13, 23, 28, 28, 28, 28, 28, 28, 28, 24, 30, 28, 28, 30, 28, 28,
        28, 28, 28, 28, 28, 28, 30, 28, 28, 28, 28, 28, 28, 28, 28, 28,
        6, 10, 10, 12, 13, 6, 8, 11, 10, 10, 8, 11, 8, 6, 6, 6,
        5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 7, 8, 15, 6, 12, 10,
        13, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
        7, 7, 7, 7, 7, 7, 7, 7, 8, 7, 8, 13, 19, 13, 14, 6,
        15, 5, 6, 5, 6, 5, 6, 6, 6, 5, 7, 7, 6, 6, 6, 5,
        6, 7, 6, 5, 5, 6, 7, 7, 7, 7, 7, 15, 11, 14, 13, 28,
        20, 22, 20, 20, 22, 22, 22, 23, 22, 23, 23, 23, 23, 23, 24, 23,
        24, 24, 22, 23, 24, 23, 23, 23, 23, 21, 22, 23, 22, 23, 23, 24,
        22, 21, 20, 22, 22, 23, 23, 21, 23, 22, 22, 24, 21, 22, 23, 23,
        21, 21, 22, 21, 23, 22, 23, 23, 20, 22, 22, 22, 23, 22, 22, 23,
        26, 26, 20, 19, 22, 23, 22, 25, 26, 26, 26, 27, 27, 26, 24, 25,
        19, 21, 26, 27, 27, 26, 27, 24, 21, 21, 26, 26, 28, 27, 27, 27,
        20, 24, 20, 21, 22, 21, 21, 23, 22, 22, 25, 25, 24, 24, 26, 23,
        26, 27, 26, 26, 27, 27, 27, 27, 27, 28, 27, 27, 27, 27, 27, 26,
        30 // EOS
    };
}